Gulf of Maine Seasonal Sea Surface Temperature Update

Seasonal Patterns in Sea Surface Temperatures

Author

Adam Kemberling

Published

September 27, 2022

About the Updates:

Over the past decade, scientists at the Gulf of Maine Research Institute have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To keep you informed, we share seasonal updates about conditions in the Gulf of Maine.

Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.

Note on Preliminary Data: This dataset has a 2-week latency period, during which values may change due to quality control measures. Any data within 14 days of the publishing date may be subject to change.

The Gulf of Maine Region

For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (Figure 1), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is displayed below. This area is consistent with previous reports and publications GMRI has produced.

For this seasonal report, we present an analysis of SST for Summer (June 1st - August 31st).

Highlights

The average SST for the Gulf of Maine during the summer (June 1st - August 31st) of 2022 was 62.14°F, making it the 3rd hottest summer on record for the period of 1982-2022 — the period over which the satellite data used are available. These temperatures are 3.89°F above the long-term (1982-2011) Summer average of 58.25°F.

Weekly Temperatures

In the below table, we highlight how the SST for each week this summer compares to a 30-year baseline period (climatological averages from 1982 through 2011).

The observed SST, long-term average SST, and SST anomalies (departures from the long-term average SST) are shown. As expected, SSTs generally rise as the summer season progresses, with anomalies showing no clear trend over the course of the season. Rather, departures from the long-term average hovered around 3°F above normal with a few weeks punctuated by anomalies exceeded 5°F.

Observed, climatological average, and deviation from the climatological average (i.e., temperature anomaly) for SST at a weekly resolution in the Gulf of Maine during summer 2022 (defined as June 1st - August 31st)
Weekly Sea Surface Temperatures - Summer
Summer (June 1st - August 31st)
One-Week Period	Observed Temperature		Climatological Average		Temperature Anomaly
One-Week Period	°F	°C	°F	°C	°F	°C
Jun 01 - Jun 04	53.5	12.0	49.6	9.78	3.92	2.18
Jun 05 - Jun 11	55.5	13.1	50.9	10.50	4.61	2.56
Jun 12 - Jun 18	57.4	14.1	52.7	11.50	4.78	2.66
Jun 19 - Jun 25	56.6	13.7	54.4	12.50	2.21	1.23
Jun 26 - Jul 02	59.3	15.1	56.2	13.40	3.09	1.72
Jul 03 - Jul 09	61.2	16.2	57.8	14.30	3.43	1.90
Jul 10 - Jul 16	62.6	17.0	59.2	15.10	3.38	1.88
Jul 17 - Jul 23	63.6	17.6	60.3	15.70	3.26	1.81
Jul 24 - Jul 30	64.8	18.2	61.3	16.30	3.47	1.93
Jul 31 - Aug 06	66.5	19.2	62.0	16.70	4.53	2.52
Aug 07 - Aug 13	67.7	19.8	62.4	16.90	5.27	2.93
Aug 14 - Aug 20	65.7	18.7	62.5	16.90	3.23	1.79
Aug 21 - Aug 27	66.9	19.4	62.2	16.80	4.66	2.59
Aug 28 - Aug 31	67.0	19.5	61.9	16.60	5.17	2.87
Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatology Reference Period: 1982-2011.

Monthly Statistics

Looking at monthly averages (as opposed to week-by-week conditions), we see each month was 3.36°F or more above the 1982-2011 climatological average. August showed the largest deviation from the long-term climatological average, with an average SST anomaly of 4.55°F.

Month	Observed Temperature		Climatological Average		Temperature Anomaly		Temperature Progression
Month	°F	°C	°F	°C	°F	°C	High/Low °F
Jun	56.5	13.6	52.8	11.6	3.75	2.08
Jul	62.9	17.2	59.5	15.3	3.36	1.87
Aug	66.8	19.3	62.2	16.8	4.55	2.53
Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatology Reference Period: 1982-2011.

Seasonal Trends and Anomalies in Context

The Gulf of Maine is an area of particular interest to the scientific community because of the remarkable rate of warming it has experienced in recent years coupled with its importance as a major driver for the regional economy.

Average annual spring SSTs in the Gulf of Maine from 1982 through 2022. The solid red line indicates the trend for the full time series.

When looking at average summer temperatures, there is a clear long-term increase, with SST’s warming at a rate of 1.06°F per decade. Recent warm Summer SST anomalies are consistent with a thermal regime shift that occurred around 2010. This rate of warming is ~4x the rate that global ocean temperatures are warming during these same months, a rate of 0.26°F per decade.

Average annual spring SSTs in the Gulf of Maine from 1982 through 2022. The solid orange line indicates the trend for the full time series for the Gulf of Maine. A solid blue line indicates the trend for the full time series for the global oceans.

This period of faster warming is part of what appears to be a distinct regime in the Gulf of Maine. The drivers of this (e.g., a weakening of the Atlantic Meridional Overturning Circulation and shifts in the path of the Gulf Stream) have been well-documented in the peer-reviewed literature, including through research by GMRI scientists.

How Does 2022 Compare?

2022 is among the warmest summers seen in the Gulf of Maine during this 41 year period. When compared against all previous summers for which we have reliable satellite data (i.e., back to 1982), this year ranks 3rd among the hottest on record. The top 5 warmest Summer have all occurred in the last decade.

An illustration of where spring 2022 ranks among the top top five warmest spring seasons on record in the Gulf of Maine. Also notable is the fact that all five warmest spring seasons on record have occurred in the last ten years.

Marine Heatwave Timeline

The most commonly used definition of a “marine heatwave” (MHW) is when daily average SST’s exceed the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Successive heatwave gaps of 2 days or less are considered part of the same event.

Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 0.95 of summer 2022 A brief reprieve in mid-May lasted less than two days, so it did not constitute a break in the heatwave event.

A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from January 2022 through August 31. Black lines representing the long-term (i.e., 1982 – 2011) average SST, the 10th percentile, and 90th percentile for a given day in the Gulf of Maine are labelled to indicate climalogical reference points; a solid line (red for marine heatwave or blue for a non-event) indicate the observed SST this year; red and blue shading illustrates how far the observed SST falls from the climatological mean.

Heatwave Anomaly Timeline

Presenting SST conditions in terms of anomalies (figure below) as opposed to absolute values (figure above) illustrates in greater detail the magnitude of MHW conditions throughout the summer.

The most extreme anomalies this summer occurred in August, with temperatures exceeding \(6°\)F above the climatological average.

A timeseries of daily average SST anomalies in the Gulf of Maine (solid red line) compared to marine heatwave (MHW) conditions (dashed black line) in the Gulf of Maine for the period January 1 through August 31, 2022.

Heatmap of Temperature Anomalies and Heatwave Events

Looking at the full record of daily SST anomalies in the Gulf of Maine (figure below), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.

Heat map of daily sea surface temperature anomalies from the beginning of 1982 through the middle of 2022. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Monthly Rankings Heatmap

Longest Heatwave on Record

This summer marked the conclusion of the Gulf of Maine’s longest heatwave event.

This event spanned from 2021-01-01 to 2022-06-19 - ultimately lasting 535 days. During that period temperatures were on average 3.87°F above temperatures observed during the 1982-2011 climate reference period.

Spatial Distribution of Seasonal Anomalies

From a spatial perspective, the Gulf of Maine and surrounding areas experienced above average SST’s for much of the region during summer 2022, but with particularly warm patches to the south and east of Georges Bank. The highest seasonally averaged anomaly of any location above was 6.73°F.

Map of average SST anomalies in spring 2022. The box outlined by the black dashed line denotes the region of study for the analysis. Darker red regions indicate stronger anomalies.

Monthly Temperature Anomalies

Average monthly temperature anomalies are displayed below. The warmest anomalies were concentrated just south of the domain studied in this analysis in June, by July SST anomalies within the Gulf of Maine were equally hot. Monthly-averaged SST anomalies in the Gulf of Maine and the surrounding areas reached > 8°F warmer than during our climate reference period (1982-2011).

This series of maps shows the average monthly SST temperature anomalies in June, July, and August 2022. The box outlined by the black dashed line denotes the region of study for the analysis. Darker red regions indicate stronger anomalies.

A work by Adam A. Kemberling

Akemberling@gmri.org